1. Field of the Invention
The present invention relates to a disk cartridge suitable for use with a disk-type recording medium, in particular a magneto-optical disk.
2. Description of the Related Art
Presently, various disk-type recording mediums are used such as magneto-optical disks, optical disks and magnetic disks. These disk-type recording mediums (referred to simply as `disks` hereinafter) are usually encased in cartridge cases for the purpose of facilitating handling of the disks in mounting or loading on demounting or unloading from disk drives, and preventing contamination of disks with dust and greasy matter on fingers.
In general, a disk cartridge has a case composed of an upper case member and a lower case member which are integrated with each other so as to define an internal space which receives a disk without restriction or constraint. In order to enable the disk in the state held in the cartridge to be mounted on a disk drive, the case is provided with an opening or openings for allowing a spindle and heads of the disk drive to be received therethrough into the case.
For instance, a disk cartridge disclosed in the specification of the U.S. Pat. No. 4,443,874 has opposing openings formed in the upper and lower case members such as to extend in the radial direction of the disk to expose a portion of the disk including the central hole of the disk. The disk cartridge also has a detachable closure member capable of closing the openings. When the disk is not used, the openings in the upper and lower case members are closed by the closure member. When the disk is to be used, the user detaches the closure member from the cartridge to expose a portion of the disk through the openings and then inserts the cartridge into the disk drive. In consequence, the spindle extends to the disk through the opening and heads are allowed to oppose the exposed portions of both surfaces of the disk.
The specification of the U.S. Pat. No. 4,608,681 discloses another disk cartridge having a case which is automatically divided or separated into a front part and rear part upon insertion into a disk drive so as to expose a portion of the disk which extends in the radial direction of the disk over a predetermined width. In consequence, the central hole of the disk receives the spindle and the heads are brought to positions where they face the surfaces of the disk.
The disk cartridge of the type disclosed in the specification of the U.S. Pat. No. 4,443,874 is disadvantageous in that it requires a troublesome work for detaching and attaching the closure member each time the disk cartridge is put to use and stored. In addition, the disk tends to be contaminated by dust and greasy matter when the closure member has been removed to enable the insertion of the cartridge or when the user has forgotten to set the closure member after the use of the disk.
In the disk cartridge of the type disclosed in the specification of the U.S. Pat. No. 4,608,681, the disk drive is required to have an internal space of a size greater than that of the disk cartridge, in order to provide a room large enough to enable the automatic separation of the front and rear parts of the case. In addition, the construction of the disk cartridge is undesirably rendered complicated and the disk drive is required to have suitable means for automatically separating the front and rear parts of the case in response to the insertion of the disk cartridge.
A disk cartridge is also known in which openings or head windows are formed in upper and lower case members and a spindle hole (hub hole) is formed in the lower case, the head windows, and hub holes being capable of being closed and opened by shutters slidable on the upper and lower cases.
In a typical example of the disk cartridge of this type, as shown in FIG. 29, a head window 15 is formed within a recess 16 formed in the surface of a case member 10, and a shutter 13 is slidable in the recess 16. Such a disk cartridge is disclosed in Japanese Patent Unexamined Publication No. 62-145586. When the above-mentioned case member 10 is the upper case member, this case member is assembled together with a lower case member so as to define an internal space which accommodates a disk 12. The lower case member is also provided with a recess and a head window similar to those of the recess 16 and the head window 15 in the upper case member. A shutter 13 has a substantially U-shaped cross-section and is slidably mounted in such a manner as to sandwich the surfaces of the recesses 16 in the upper and lower case members. The recesses 16 in the upper and lower case members are provided with guide grooves 17 which are formed in the vicinity of the sides 11 of the case members 10 in parallel therewith. Claws 13a provided on the inner surfaces of the shutter 13 engage with the guide grooves 17 such as to allow the shutter 13 to slide in parallel with the side 11. The shutter 13 is biased by a spring 13 so that the head windows 15 are normally closed, as illustrated. When this disk cartridge is inserted into the disk drive, an actuating means operates to drive the shutter 13 to the right as viewed in the Figure against the force of the spring 18, thereby allowing the head windows 15 to open.
The recesses 16 are intended to limit the range of movement of the shutter 13. When the head windows 15 are closed, the shutter 13 contacts at its one side (left side) with the corresponding side (left side) of the recesses 16, whereas, when the head windows are opened, the other side (right side) of the shutter 13 is stopped by the corresponding side (right side) of the recess 16.
The shutter should have a length and a width large enough to cover the head windows. In the arrangement shown in FIG. 29, the shutter 13 is made to have a width considerably greater than the width of the head window 15 at its end adjacent to the side 11, while the other end of the shutter 13 has a width which is slightly greater than the width of the head window 15, so that the shutter 13 generally has a substantially right-angled triangle form. The guide grooves 17 do not extend to the region intermediate between the head window 15 and the side 11, while the claws 13a are provided rather adjacent to the right end of the shutter 13.
Japanese Patent Unexamined Publication No. 61-211888 discloses a shutter which has a substantially rectangular form with a width somewhat greater than that of the head window 15. This type of shutter is applicable to the arrangement of FIG. 29, provided that the recess 16 has a correspondingly rectangular form and that the guide grooves 17 are extended into the region intermediate between the side 11 and the head window 15.
In some of disk cartridges which incorporate a shutter of the type mentioned above, the shutter is designed to cover also the hub hole for receiving the spindle. In such a disk cartridge, the shutter is required to have a substantial width because the hub hole has a considerably large diameter so that the stroke of the shutter is increased correspondingly. Since the shutter width is increased, the width of the head window also tends to be increased in order to facilitate the access of the head to the disk.
The shutter is usually biased by a spring member so as to normally close the head windows and the hub hole. If an abnormal external force produced, for example, by a touch of a finger is exerted on the shutter, the shutter can easily move against the force of the spring member. Since the shutter width is only slightly greater than the width of the head window, the head window is opened even by a slight movement of the shutter. If the head window width is determined to be slightly greater than the width which is actually required, the head window is opened even by a very small movement of the shutter, thus enhancing the risk for the disk to be contaminated by dust or greasy matter, with the result that the reliability is impaired undesirably.
In order to avoid undesirable contact and interference between the heads and the disk cartridge during insertion into the disk drive, the surfaces of the case are recessed in the form of steps at portions between the side 11 of the case and the respective head windows 15 to reduce the thickness of the cartridge at this portion. FIG. 30 shows a known cartridge which makes use of a rectangular shutter 13 and which has steps or recesses 19 in the surface portions between the side 11 and the head windows 15. It is impossible to form the guide grooves 17 in this recess 19. When this recess 19 is provided in a disk cartridge which has a large window width (length in the direction parallel to the side 11), one of the claws 13a provided inside the shutter 16 undesirably floats in the recess 19 so that the left portion of the shutter loses the support thereby allowing the shutter 13 to play or rattle.
In general, the disk cartridge with the head windows closed by the shutter 13 is taken out of the disk drive and, hence, has a large risk to be subjected to abnormal external force. The shutter 13 without support has a very small mechanical strength and tends to be damaged by an impact.